Search PubMed⌕ Search

Biomedical subjects

M L Urken

Publications and source records attributed to M L Urken.

At least 55 records · Page 3Linked to original sources
PubMed1996

Combination therapy for salvaging a failing, experimental skin flap.

The failing free flap remains a major problem for the reconstructive surgeon. Many and varied pharmacologic agents have been utilized to reverse the effects of ischemia in these flaps. Treatments have been aimed at inhibiting presumed causative factors in the no-reflow phenomenon. Therapy has generally been single in nature and designed to affect only one of these presumed factors. In this study, several pharmacologic agents were utilized individually or in combination therapy as postischemic washouts, in an effort to attack the multiple causative factors in the no-reflow phenomenon and to improve flap survival in a rat abdominal skin flap model. The treatment agents included lactated Ringer's, superoxide dismutase, and urokinase, with each used independently as a postischemic perfusion washout. Combination therapy utilized an initial postischemic perfusion with urokinase, followed by a second perfusion washout with superoxide dismutase. After 18 hr of primary ischemia, there was increased flap survival in the animals undergoing perfusion washout with either superoxide dismutase alone or with combined urokinase and superoxide dismutase washouts, compared to all other treatments (p < 0.001). It was found that flaps undergoing combined urokinase and superoxide dismutase postischemic perfusion washouts demonstrated significantly improved survival after 20 hr of primary ischemia, compared to all other therapies (p < 0.05). By demonstrating improved survival when a thrombolytic agent is used in conjunction with an oxygen free radical scavenger, these findings may have implications in the treatment of clinically failing free flaps.

Animals↗
PubMed1996

Reappraisal of the inferior epigastric flap: a new neurovascular flap model in the rat.

An anatomic, histologic, and electrophysiologic study was carried out in order to determine the distribution and cutaneous sensory territory of the epigastric nerve in the rat. Results for nerve staining (Sihler's method) and electrophysiologic nerve mapping indicate that the neurosome of the epigastric nerve has a different autonomy than the vascular territory of the inferior epigastric artery. Based on these findings, an experimental model for neurovascular free-tissue transfer is proposed.

Abdomen↗
PubMed1995

Rigid fixation of vascularized bone grafts in mandibular reconstruction.

OBJECTIVE: To evaluate the nature of complications and complication rates with the use of three different reconstruction plates for the rigid fixation of vascularized bone grafts in oromandibular reconstruction. DESIGN: We conducted a case series of 95 patients over a 6-year period, with a minimum follow-up of 6 months and a maximum follow-up of 66 months. SETTING: Academic tertiary referral medical center. PATIENTS: Forty-eight patients had vascularized bone grafts fixated to native mandible with AO stainless steel reconstruction plates; 25 patients, with AO titanium plates; and 22 patients, with titanium hollow screw reconstruction plates (THORPs). Types of vascularized flaps, mandibular defects to be reconstructed, and use of radiation therapy were similar among the three groups. INTERVENTION: The surgical approach involved oromandibular reconstruction with a vascularized bone graft rigidly fixated with a reconstruction plate. OUTCOME MEASURES: Clinically and radiographically noted complications and resultant treatment. RESULTS: In the grafts fixated with AO stainless steel reconstruction plates, three plate fractures, seven instances of loose screws, eight plate exposures, and two cases of nonunion occurred. No cases of plate fracture or nonunion occurred in the titanium or THORP groups. One titanium plate and two THORPs were exposed during the study period. One instance of loose screws occurred in the titanium group; none in the THORP group. Seventy-four percent of those complications occurred within 12.4 months (the mean follow-up time of the THORP group). The incidence of complications in the stainless steel group was significantly greater than that in the titanium or THORP groups. No statistically significant increase in the rate of complications was noted when radiation therapy was used as a component of treatment. CONCLUSIONS: To our knowledge, this is the first study to compare three different reconstruction plates for fixation in vascularized bone reconstruction of the mandible. AO THORPs are now used almost exclusively to rigidly fixate vascularized bone grafts because of their advanced design and their potential for osseointegration and because fewer screws are necessary to attain adequate fixation than with conventional AO reconstruction plates.

Adult↗
PubMed1995

The restoration or preservation of sensation in the oral cavity following ablative surgery.

The importance of sensory feedback from the oral cavity is evaluated in the context of functional rehabilitation following ablative surgery using three techniques that restore or preserve sensation. Nerve grafts to restore the continuity of sensory nerves interrupted during ablative surgery, as well as the role of sensate flaps and the protection of palatal sensation following soft palate resection or total glossectomy, are discussed.

Feedback↗
PubMed1995

Free flap monitoring: a review of current practice.

Individual techniques for the postoperative monitoring of free flaps vary considerably. In order to establish the currently preferred protocols, a survey was conducted among micro-surgeons in North America using a mailed questionnaire. Data were received from 95 centers for the monitoring of 2,825 free flaps performed during 1994. Results indicate that rates for flap salvage and overall success with free tissue transfer are closely related to surgical experience (number of cases performed per month). Ninety percent of microsurgeons routinely use monitoring devices, with external and laser doppler having achieved greatest popularity. An account is given of the preferred postoperative regimens for flap surveillance, and the overall results are discussed.

Clinical Competence↗
PubMed1995

Glutathione disulphide as a marker of reperfusion injury in ischaemic skin flaps.

Estimation of the oxidised form of glutathione (GSSG) in an ischaemic/reperfused organ is frequently employed as an indicator of oxidative stress created by the production of oxygen free radicals during the reperfusion period. The time course of oxidative stress and tissue damage in 19 ischaemic/reperfused guinea-pig island skin flaps was evaluated. No-flow ischaemia was induced in the flaps for 6 h in 7 animals, and for 8 h in 9 animals (a further 3 animals served as controls without ischaemia). Arterial and venous blood samples were obtained directly from the flap pedicle at baseline, 10, 30, and 60 min following reperfusion. Results suggest that a second focus of oxidative injury, possibly mediated by activated neutrophils, contributes to the overall process of reperfusion injury. Plasma levels of GSSG allow for a more sensitive quantification of oxidant stress within reperfused ischaemic flaps, and may serve as a useful tool in skin flap research.

Animals↗
PubMed1995

Use of the guinea pig flank flap in skin flap research.

A variety of flaps in laboratory animals have been designed that propose to parallel the behavior of human skin under different experimental conditions. In the search for a readily available and affordable island skin flap model that combines reliable anatomy with a pedicle of substantial size, we have designed in the guinea pig a cutaneous flap based on the superficial circumflex iliac artery and vein. In 22 adult female Hartley guinea pigs, an 8 x 4 cm flank flap based on the superficial circumflex iliac pedicle was raised, and its characteristics were evaluated for applications to skin flap research. Dermofluorometric studies were performed that confirm the vascularity of this flap, and 100% survival of the flap was seen 5 days after surgery in all animals. Of particular benefit was the demonstration that both afferent and efferent blood samples can be taken from the pedicle directly, which allows for the direct quantification of plasma markers after physiologic insults to the skin flap, such as burn or ischemia. This anatomically reliable and easily dissected flap lends itself well to preliminary skin flap research and may contribute to standardization of a model for further studies examining the behavior of skin microcirculation under adverse physiologic conditions.

Animals↗
PubMed1995

Improved efficacy of urokinase further prolongs ischemic skin-flap survival.

Salvage of a free-tissue transfer, when postoperative vascular compromise is detected, depends largely upon the restoration of a patent microcirculation. The therapeutic efficacy of thrombolytics infused directly into the failing flap has been clearly demonstrated. In this experiment, the authors investigated whether the method of selective administration of urokinase to failing skin flaps in 68 Sprague-Dawley rats had any effect on flap survival. In one group of animals, postischemic flaps were perfused with 100,000 IU of urokinase given by manual injection, and via a pressurized delivery system (150 mmHg) in the other group. Flap survival was assessed at 7 days. A significantly greater survival was seen in flaps treated with urokinase by controlled pressure infusion (p < 0.01). This simple method is suggested to increase the efficacy of urokinase used in the context of flap salvage.

Animals↗
PubMed1995

Evaluation of a continuous systemic infusion of iloprost, a stable PGI-2 analog, on the survival of experimental skin flaps.

Numerous investigators have attempted to enhance the survival of ischemic experimental skin flaps using various pharmacologic manipulations. Recently, the authors' laboratory demonstrated the beneficial effect of iloprost, a stable PGI2 analogue, as a post-ischemic perfusion washout, in improving the survival of ischemic skin flaps. The rat unilateral abdominal skin flap, based on the superficial epigastric vessels, was utilized in this study involving 30 animals. The animals were divided into three different treatment groups, with ischemic periods of 16 and 18 hr. Perfusion washouts were performed at the completion of the various ischemic periods. Alzet osmotic pumps were used to deliver a continuous systemic infusion of iloprost for 7 days postoperatively. The groups consisted of the following: Group 1 (single ILO)--perfusion washout with iloprost only; Group 2 (continuous LD ILO)--low-dose systemic iloprost infusion (0.066 mcg/kg/min) and perfusion washout with iloprost; and Group 3 (continuous HD ILO)--high-dose systemic iloprost infusion (0.1 mcg/kg/min) and perfusion washout with iloprost. The percentage of flap survival was assessed on postoperative day 7. Skin flaps of the animals receiving the continuous systemic infusion of iloprost were noted to have varying percentages of survival, while skin flaps undergoing perfusion washout only were found to have either complete survival using a continuous systemic infusion of iloprost, compared to iloprost perfusion washout alone. In addition, the hypotensive side effects of systemic iloprost infusion limit its use in the rat skin-flap model.

Animals↗
PubMed1995

Additional benefit of heparin in the thrombolytic salvage of ischemic skin flaps.

Microvascular thrombosis is known to play an important part in the cessation of flow seen in a flap following ischemia and revascularization. Its reversal, using thrombolytic therapy, is associated with higher rates of successful flap salvage. Although this procedure restores patency to the microcirculation, the damaged endothelial cell layer remains highly thrombogenic and a definite risk of rethrombosis exists in the early period of reperfusion. In an inferior epigastric flap model in a rat, we investigated the effect of additional heparin (subcutaneous and intravenous administration) following a standardized urokinase washout (100,000 iu) of the ischemic flaps. Flap survival was assessed at 1 week and morphological changes in the microcirculation were observed using electron microscopy. Results showed a significant increase in flap survival in the group receiving intravenous heparin following urokinase washout and suggest that systemic heparin may play a beneficial role in the early reperfusion period following thrombolytic flap salvage.

Animals↗
PubMed1994

A new bilobed design for the sensate radial forearm flap to preserve tongue mobility following significant glossectomy.

OBJECTIVE: A new bilobed design of the sensate radial forearm flap is presented for reconstruction of the oral cavity following significant glossectomy. One lobe of the flap is used to restore the shape and volume of the tongue, while the second lobe is used to resurface the floor of the mouth and the gingiva. SETTING: Tertiary referral center. PATIENTS: Ten patients who underwent significant glossectomy for squamous cell cancer were included in this study. Patients were deemed candidates for this form of reconstruction when at least one half of the mobile tongue was resected and the residual tongue had an intact motor nerve supply. RESULTS: In addition to the thin, pliable, and sensate tissue of the radial forearm skin, the bilobed design helps to prevent tethering of the root of the tongue to the inner table of the mandible. This factor is felt to be important in maximizing the mobility of the residual tongue. There were no flap failures or partial necroses. Tongue mobility, oral alimentation, articulation, and return of sensation are described.

Adult↗
PubMed1994

Vascularized bone flaps in oromandibular reconstruction. A comparative anatomic study of bone stock from various donor sites to assess suitability for enosseous dental implants.

OBJECTIVE: To identify donor sites from which vascularized bone may be harvested capable of accepting osseointegrated implants of the minimum dimensions required to ensure long-term implant stability. DESIGN: An anatomic study of the most commonly employed donor sites for vascularized bone in oromandibular reconstruction was conducted on 28 cadavers. SETTING: Academic tertiary referral center. PARTICIPANTS: Twenty-eight freshly embalmed, adult white cadavers (16 male, 12 female) were dissected. INTERVENTION: The ipsilateral fibula, iliac crest, radius, and lateral border of the scapula were harvested and multiply sectioned at predetermined sites. OUTCOME MEASURE: Implantability was determined for each section based on measurements of height, width, and cross-sectional area utilizing computer planimetry. RESULTS: The iliac crest was the most consistently implantable donor site, followed by the scapula, fibula, and radius (83%, 78%, 67%, and 21% of sections from each donor site satisfying the criteria for implantability). Consistent regional differences in implantability were encountered at each donor site except the scapula. CONCLUSIONS: Following ablation of oromandibular malignant neoplasms, restoration of stable retentive dentition is a prerequisite to a successful functional oral rehabilitation. This is best achieved with enosseous implants, capable of supporting a stable dental prosthesis, placed directly into vascularized bone flaps at the time of mandibular reconstruction. The implications of the results obtained in this study for gender, donor site selection, and orientation of the vascularized bone flap are discussed.

Aged↗
PubMed1994

A systematic approach to functional reconstruction of the oral cavity following partial and total glossectomy.

Mobility, sensation, volume, and to a lesser extent, the shape of the tongue following partial glossectomy are critical elements to the successful rehabilitation of the patient with oral cancer. Our approach to tongue reconstruction is based on the extent and functional status of the residual tongue and whether there is an associated mandibulectomy. Despite the devastating effects of ablative surgery and radiation, the application of available reconstructive techniques can help to improve the quality of life of these patients. Herein, we present a revised classification scheme for tongue defects along with a discussion of the optimal method for reconstruction based on available techniques.

Adolescent↗
PubMed1994

Microvascular free flaps in head and neck reconstruction. Report of 200 cases and review of complications.

OBJECTIVE: Microvascular free-tissue transfer to the head and neck has become an accepted method of reconstruction owing to increased success rates and superior aesthetic and functional results. Although the large number of arteries and veins in the neck make free-flap revascularization easier than in other recipient sites of the body, there are also unique problems that pose significant risks to the success of the procedure. We report our experience with 200 microvascular free flaps performed between 1987 and 1992. SETTING: This study was conducted at a tertiary referral center. PATIENTS: The majority of patients in this series underwent surgery for squamous cell cancer. Approximately 75% of the reconstructions were performed for defects of the oral cavity. There were 120 vascularized bone-containing free flaps for mandibular and midface reconstruction. The remaining 80 soft-tissue flaps were used for a variety of defects ranging from the scalp to the pharyngoesophagus. RESULTS: An overall success rate of 93.5% for free-tissue transfers is reported. Greater experience with this technique has resulted in a reduction and a change in the nature of the complications encountered compared with those seen in the early part of our series. Donor and recipient site complications, including flap failures and anastomotic revisions, are analyzed in detail with respect to age, radiation status, donor site, and whether the ablative procedure was done for a primary or recurrent neoplasm.

Adolescent↗
PubMed1994

Simultaneous interstitial radiotherapy with regional or free-flap reconstruction, following salvage surgery of recurrent head and neck carcinoma. Analysis of complications.

OBJECTIVE: Reports on complications following brachytherapy offer conflicting views on the benefit of locoregional flap coverage of the implanted tumor bed. This study reviews complications following pedicled and free-flap coverage of brachytherapy sources after salvage surgery for recurrent head and neck carcinoma. DESIGN: Retrospective chart review. SETTING: Academic tertiary referral center. PARTICIPANTS: Fifteen patients with advanced, radiorecurrent carcinomas of the head and neck, treated between 1988 and 1992. INTERVENTION: All patients underwent surgical resection and implantation of the tumor bed with iridium 192 after-loading catheters (13 patients) or iodine 125 seeds (two patients). The average dose of interstitial radiotherapy supplied was 50.24 +/- 45.19 Gy (mean +/- SD). Coverage of the implanted tumor bed was achieved with regional myocutaneous flaps in 10 patients and microvascular free flaps in five patients. OUTCOME MEASURE: All wound and healing complications were identified. Patients were followed up for a minimum of 3 months. RESULTS: No significant complications were encountered. No flap, pedicled or free, demonstrated any degree of necrosis. Four minor complications developed in the group of patients who underwent reconstruction with pedicled myocutaneous flaps. One orocutaneous fistula developed in a patient in whom a radial forearm was used to reconstruct a posterior pharyngeal wall defect. CONCLUSIONS: An expectation of increased postoperative morbidity should not interfere with the decision to proceed with multimodality salvage therapy of patients with advanced, recurrent head and neck tumors. The advantages of free tissue transfer in the reconstruction of head and neck defects are not compromised when the flaps are simultaneously utilized to provide coverage for brachytherapy sites.

Adult↗
PubMed1994

Craniofacial resection. An analysis of 73 cases.

OBJECTIVE: To determine the morbidity and mortality associated with a large series of patients undergoing craniofacial resection at one institution. The series is also analyzed with respect to pathology, disease recurrence, and role of adjuvant therapy. DESIGN: Retrospective review with a mean follow-up of 3 years (range, 6 months to 8 years). SETTING: Tertiary care, urban referral center. PATIENTS: The study included 73 consecutive patients (39 male and 34 female). Ages ranged from 13 to 78 years with a mean of 53.1 years. All patients had benign or malignant tumors of the paranasal sinuses. MAIN OUTCOME MEASURES: Morbidity associated with craniofacial resection was categorized as follows: early (within 30 days of surgery) or late (> 30 days); neurologic, ocular, or infectious. RESULTS: Overall morbidity rate was 63%, and the mortality rate was 2.7%. Of the patients who had complications develop, 26 had development of major morbidities and there were two mortalities. The most common complications were transient alteration in mental status (15 patients), diplopia (11 patients), cerebrospinal fluid leak (10 patients), and osteomyelitis of the frontal bone flap (eight patients). CONCLUSIONS: Craniofacial resection is an effective surgical treatment for paranasal sinus tumors. The mortality rate is acceptable and morbidity appears directly related to experience with the procedure. Infectious complications were the most devastating.

Adolescent↗
PubMed1994

A modified design of the buried radial forearm free flap for use in oral cavity and pharyngeal reconstruction.

OBJECTIVE: We present a new design for the radial forearm flap that includes a small monitor segment that is connected to the primary skin paddle by a fascial subcutaneous segment of tissue. This design modification permits buried flaps to be easily monitored and provides vascularized tissue coverage of the flap vessels as well as the great vessels in the neck. Immediate augmentation of the radical neck deformity can be achieved. SETTING: This study was conducted at a referral center. PATIENTS: Fifteen patients with squamous cell cancer of the pharynx and tongue base were included in this study. The defects in these patients were judged to be best reconstructed with a radial forearm free flap. RESULTS: All free flaps in this series survived. There was one case, described in detail, in which the fascial subcutaneous portion of the flap was exposed to salivary contamination. The flap vessels remained well protected and flap viability was unimpaired.

Adult↗